Many applications exist for effecting electrical contact between two conductors. An application includes interconnection between the leads of an integrated circuit device and conductive pads or terminals on a printed circuit board which serves as an interface between the integrated circuit device under test and the tester apparatus.
Both electrical and mechanical considerations are necessary to design an interconnect between an integrated circuit and the printed circuit board, also known as a load board. One of the mechanical considerations to be taken into account in designing an interconnect system is that a wiping action should be accomplished between the contact itself and the lead of the integrated circuit by which the contact is engaged. The wiping action functions to effect maximization of effective contact in view of oxide build-up which can occur on the lead of integrated circuit. In effect, the wiping action enables a good interface to be accomplished between the contact and the lead of the integrated circuit. Electrical considerations for such an electrical interconnect contact system include that the contact should be a high-speed, short path device. In addition, the contact should have a low inductance without having a controlled impedance requirement.
One example of an electrical interconnect contact system designed to address the problems associated with designing an interconnect between the leads of an integrated circuit device and a printed circuit board is shown in U.S. Pat. No. 5,069,629. The electrical interconnect assembly disclosed in the '629 patent includes a housing which is interposed between the lead of the integrated circuit and the corresponding spaced terminal of the printed circuit board. The housing is provided with slots extending from a first surface to an opposite surface and has troughs formed on the surfaces of the housing. A first rigid element is received in the trough formed on one surface and extends across slots in which one or more contacts are received. An elastomeric second element is received in the trough formed in the second surface of the housing and extends across the slots in which contacts are received. The elastomeric elements are provided with the measure of compressability and tensile extendability. A planer contact is received within the slots and has a protruding contact surface extending from either end to contact the lead of the integrated circuit and the pad on the printed circuit board.
Disadvantages with the design embodied in the '629 patent is that the contact provides an extremely small amount of travel, 0.008 inches, which leaves little room for error. This is particularly problematic when you consider there is a very small amount of room available for interconnection between the leads on an integrated circuit and the contact pads on the load board. A second disadvantage is that the load board is quickly worn out because of wiping action of the device at both the integrated circuit lead and the load board pads. Considering the integrated circuits are continually cycling through the test and being changed a single wipe is advantageous, however, the load board is continually used throughout the repeated testing of integrated circuits and therefore the constant wiping wears out the load board.
Consequently, a need exists for a semiconductor electromechanical contact which addresses the problems associated with prior contact devices and is inexpensive to manufacture.